Experimental Investigation On The Effect Of Top Gas Injection-assisted Gravity Drainage In Porous Carbonate Reservoir

In recent years,the technology of gas injection to enhance oil recovery has developed rapidly and gradual become an important technology in oilfield development.Among them,the top gas injection-assisted gravity technology has a better development prospect,which combines the best of all worlds of gas and gravity drainage.So it is urgent and important to study its development effect and related oil displacement mechanism.In this paper,with the porous carbonate reservoir as the research object,the top gas injection-assisted gravity drainage was studied by means of laboratory physical simulation experiment and other technical methods.In the first place,the onedimensional long-core displacement experiment was carried out to study the oil displacement effect of different methods and the influencing factors of top gas injectionassisted gravity;After that,aiming at the target reservoir,the 3d physical model was designed and made,the simulation experiments of different development methods were carried out to compare the effect of top gas injection-assisted gravity in the actual reservoir.The results show that:(1)Compared with the traditional gas drainage,the top gas injection-assisted gravity delay the steam breakthrough time,and it can still maintain a high oil production rate after gas breakthrough.So its stable production time is more longer,and the ultimate recovery rate reached 54.4 %,the oil displacement effect is better than other gas drainages.(2)Dip Angle are positive correlated with the development effect;The gas injection velocity and crude oil viscosity are negatively correlated with the development effect.The positive rhythmic formation is unfavorable to the development effect,while the negative rhythmic formation is favorable to the development effect.(3)In the target reservoir development,compared with other methods,top gas injection-assisted gravity can maintain reservoir pressure,make full use of gravity differentiation,maintain oil and gas interface stability,oil recovery increased by 6%,achieve a better development effect.